There are a wide variety of high-temperature process vessels which have a refractory material layer on the inside surface thereof. Examples include rotary kilns, including cement kilns and the burner pipes therein, mineral processing kilns, glass furnaces, copper smelters, aluminum smelters, vertical channel furnaces in foundries, and various steel making vessels. Such vessels, which have a steel shell and a refractory lining on the inside surface thereof, are subjected to temperatures up to 3000.degree. F. or higher. In the construction of these vessels, typically a pattern of metal stud welded anchors are affixed to the steel shell of the kiln and a ceramic refractory lining is cast or bricked into place on the inside surface of the steel shell. The metal stud welded anchors retain the ceramic refractory lining on the inside surface of the kiln.
During use, the kiln or other high temperature process vessel is subject to significant temperature cycling which may cause cracking or deterioration of the refractory lining. In addition, the action of the material being processed, such as in a cement kiln, erodes the refractory lining. In fact, at some point the refractory lining crumbles or wears away and exposes the steel shell of the vessel. In order to repair the refractory lining, it may be necessary to affix a metal anchor to the shell wall by stud welding or some other welding technique and then apply ceramic refractory material at that location to complete the repair of the lining. One such technique for affixing metal anchors to the vessel shell is stud welding. This is a well known process and the necessary equipment, stud welding guns, are readily available.
Heretofore, due to limitations of available welding apparatus, including stud welding apparatus, the kiln must be shut down from operation and cooled to a temperature sufficiently low that an operator can enter the kiln and perform the repair, which may or may not involve stud welding of one or more metal anchors, and thereafter apply the refractory to repair the kiln lining. The repair may utilize the well known technique of ceramic welding or gunning. Shutting down a kiln and cooling it to a sufficiently low temperature to permit an operator to enter and perform the repair is exceedingly time consuming, and therefore costly. More particularly, due to the amount of down time of the kiln, significant revenue is lost based on lost throughput. Moreover, significant energy costs are associated with cooling down and reheating kilns for purposes of repair. Additionally, the actual cooling of the kiln may result in further damage due to the temperature cycling that it creates.
What is needed is an apparatus that permits the repair of process vessels, such as kilns, while at or near their operating temperatures and which requires only a small downtime in their usage.